Trace

新项目生产测试接口，报错OOM

org.springframework.web.util.NestedServletException: Handler dispatch failed; nested exception is java.lang.OutOfMemoryError: Java heap space
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1054)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005)
        at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
        at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at com.mfw.flight.server.filter.RequestResponseLogFilter.doFilter(RequestResponseLogFilter.java:70)

因为是搜索场景，以为是结果太多导致，

修改结果大小，1000改到200，无效。

修改heap大小，4G改到8G，无效。

决定在请求的时候，实时dump出内存看下。

jmap -dump:live,format=b,file='/tmp/dump.hprof' 1

下载dump文件到本地，安装mat分析工具，打开mat，导入dump文件，查看Leak Suspects

其中a占了2.3G，看着是问题来源，查看stacktrace

定位到buildFullName，查看代码

private String buildFullName(Mdd mdd, Map<Long, Mdd> parentMddMap) {
        StringBuilder fullName = new StringBuilder();
        fullName.append(mdd.getMddNameChn());

        Long parentMddId = mdd.getParentMddId();
        int loops = 0;
        do {
            Mdd currentMdd = parentMddMap.get(parentMddId);
            if (Objects.isNull(currentMdd)) {
                break;
            }
            if (currentMdd.getMddTypeCode().reachContinent()) {
                break;
            }

            fullName.append(", ").append(currentMdd.getMddNameChn());

            parentMddId = currentMdd.getParentMddId()

        } while (Objects.nonNull(parentMddId) && parentMddId != 0L);

while循环！所以可能是这里出现死循环了，加日志，发现存在parent_id=当前ID的情况（脏数据），导致死循环。修复，问题不再复现。

反思

while循环考虑异常情况（不要对数据完全信赖）